Hello, I'm working on a KRK powered speaker pair that uses the 2SC3281/2SA1302 pair for its amp. I need to replace ONE of the transistors as it blew do to my screw up :-(
Details worth noting:
1. I have LOTS of MJL1302A and MJL3281A's
2. I have the tools / ability to test HFE.
3. The schematic actually CALLS for the MJL's and not the 2SA/2SC's. *schematic attached.
4. The pairs that were in the amp do not appear to be all that well matched. Testing one set out of 4 total (there are 2 speakers and each speaker is bi-amp for a total of 4 amps) yielded HFE's of 120-100 on the 2SC's and 65-65 on the 2SA's
5. The error that I made was replacing a driver with the wrong type. *See attached schematic.
QUESTIONS / HELP NEEDED:
1. Should I just replace all the output transistors with the MJL's that I have, matched as well as I can?
2. IF 1. = YES, then does everything else (drivers transistors, Emitter resistors, etc.) work as is? i.e. Are the MJL's "drop in" in the truest sense of the phrase?
3. Should I just replace the ONE shorted 2SA1302 with a MJL1302A and leave the rest alone? Cause it's a true "drop-in" and I'll be fine?
4. Should I just replace the pair as the 2SC was probably stressed during my error?
5. If 4 = yes, then replace it with a MJL3281A?
6. How important is matching HFE?
6A. All of my MJL3281A's read about 99 HFE. BUT all of my MJL1302A's read about 79 HFE. Great matching for each PNP / NPN type, but not NPN to PNP if that makes sense.
6B. Does that matter?
Details worth noting:
1. I have LOTS of MJL1302A and MJL3281A's
2. I have the tools / ability to test HFE.
3. The schematic actually CALLS for the MJL's and not the 2SA/2SC's. *schematic attached.
4. The pairs that were in the amp do not appear to be all that well matched. Testing one set out of 4 total (there are 2 speakers and each speaker is bi-amp for a total of 4 amps) yielded HFE's of 120-100 on the 2SC's and 65-65 on the 2SA's
5. The error that I made was replacing a driver with the wrong type. *See attached schematic.
QUESTIONS / HELP NEEDED:
1. Should I just replace all the output transistors with the MJL's that I have, matched as well as I can?
2. IF 1. = YES, then does everything else (drivers transistors, Emitter resistors, etc.) work as is? i.e. Are the MJL's "drop in" in the truest sense of the phrase?
3. Should I just replace the ONE shorted 2SA1302 with a MJL1302A and leave the rest alone? Cause it's a true "drop-in" and I'll be fine?
4. Should I just replace the pair as the 2SC was probably stressed during my error?
5. If 4 = yes, then replace it with a MJL3281A?
6. How important is matching HFE?
6A. All of my MJL3281A's read about 99 HFE. BUT all of my MJL1302A's read about 79 HFE. Great matching for each PNP / NPN type, but not NPN to PNP if that makes sense.
6B. Does that matter?
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If it was me, keep in mind I’m not a professional repair person only hobbyist, I would change just the shorted 1302A and wouldn’t worry about matching. As long as they others test okay, which sounds like you have done that.
Be sure and check back one level to make sure no other transistors or resistors failed from the stress.
Be sure and check back one level to make sure no other transistors or resistors failed from the stress.
Don't forget to recheck the bias point after changes like this.
The hfe values are often measured at low current by testers, this usually isn't the actual gain that you'll see at amp levels of current (gain drops at both low current and high current), and ~1mA is a tiny current for an output transistor and the hfe values you are getting are probably only rough guides unless your tester uses an amp or so.
The hfe values are often measured at low current by testers, this usually isn't the actual gain that you'll see at amp levels of current (gain drops at both low current and high current), and ~1mA is a tiny current for an output transistor and the hfe values you are getting are probably only rough guides unless your tester uses an amp or so.
Its only a pair of PNP outputs
I would just change both to the same manufacture
Far as the 2n5551
Standard 5551 should be CBE
If there is a C suffix then the collector is center or ECB
I would just change both to the same manufacture
Far as the 2n5551
Standard 5551 should be CBE
If there is a C suffix then the collector is center or ECB
If I understand you have one shorted 2SA1302 on the Neg rail.
Which uses 2 output devices on that rail.
Just replace both with MJL1302
From the fault that happened one transistor did fail.
As far as the health of the other one...who knows.
Just replace both
Which uses 2 output devices on that rail.
Just replace both with MJL1302
From the fault that happened one transistor did fail.
As far as the health of the other one...who knows.
Just replace both
The 2SA and MJL types are similar but not exactly the same. Different enough where you don’t want to mix and match when paralleling them (replace both) but similar enough to use 2SC on top and MJL on bottom. For single digit ppm distortion amps with extreme attention to detail you would use the same and match hFE between NPN and pnp. For something like this it’s just not that critical.